Two loose ends in the cosmological lithium problem: the interstellar lithium abundance toward Sk 143, and the 7Be(γ,α) and 7Li(γ,α) rates in ACROPOLIS

This note examines two inputs that recent work uses to argue about the cosmological lithium problem. (i) Interstellar lithium toward Sk 143 (AzV 456). This is the only Small Magellanic Cloud sightline with interstellar Li I. Two published analyses give A(Li) = 2.68 and 2.16. We show that they agree on the measured Li/K ratio: the whole 0.5 dex difference comes from the potassium abundance each adopts for the absorbing cloud. The Zn II and S II lines were already known to be saturated. We refit the archival HST/STIS Zn II and S II absorption with the Doppler parameter b free, to quantify what that saturation allows. We recover the published N(Zn II) at the published b = 1.6 km/s, but the data do not determine b for the cold component. Depending on the component model, the likelihood is bimodal or nearly flat. Without a physical bound, N(Zn II) is uncertain by more than an order of magnitude at 95% confidence. With [S/H] ≤ 0 imposed, which of the primordial value and the stellar plateau is allowed depends on the conversion conventions; under the published conventions the primordial value is excluded only marginally. With existing data this sightline cannot distinguish the two. (ii) The ACROPOLIS photodisintegration code. The public code ACROPOLIS (all releases through 1.3.1) implements analytic fits for 7Be(γ,α)3He and 7Li(γ,α)t that are about 3 times larger than detailed balance applied to the radiative-capture S-factors. Ishida, Kusakabe & Okada (2014) had already identified this discrepancy for the underlying fits. For photon injection below the deuterium threshold, the decaying-particle abundance needed for a given 7Li reduction is underestimated by a factor of 2.6–3.8. This shifts the lithium-solution regions of Depta, Hufnagel & Schmidt-Hoberg (2021), but not their D, 3He and 4He limits. Neither result is a new measurement of primordial lithium. Both are corrections of scope and bookkeeping. The code and numerical outputs are included in the accompanying zip archive.